This invention concerns check valves and more particularly check valves for use in aerosol dispenser packages which employ compressed rather than liquified gas propellants.
Preferably, packages of this kind will involve a regular as well as an ON/OF actuator valve, the regulator serving to control product dispensing from the package to a generally constant flow rate. In the absence of such regulation the flow rate will initially be high and thereafter progressively reduce, with the propellant pressure, as product is dispensed from the package and the propellant expands to fill the package. This is not compatible with the maintenance of a consistent spray pattern and other discharge characteristics appropriate for many of the products made available in aerosol dispenser packages.
One proposal for a regulator for this purpose is described in Patent Specification GB 2,216,634A.
In any event, whether the package includes a flow regulator or not, it is desirable that an additional check valve be provided to reduce the loss of propellant which can otherwise occur with actuation of the package when tilted significantly from an upright disposition. In this connection it is to be noted that the actuator valve will normally communicate with the package interior by way of a dip tube of which the free end is located in the lowermost region of the package to be submerged in the product substantially throughout total dispensing of the latter with the package upright. Inversion of the package will, of course, expose the free end of the dip tube to propellant gas and actuation in these circumstances simply releases such gas to atmosphere to no useful end. In fact such actuation is counterproductive in that it can lead to an exhaustion of propellant before the product in the package has been substantially wholly dispensed, and such a situation can occur more readily with use of a compressed gas propellant which is an inherently more limited resource for a given package and product volume than is the case for a liquified gas propellant. Moreover, such a loss of propellant can occur with a lesser inclination of the package relative to the upright disposition as the product volume remaining in the package is progressively reduced by discharge.
The above-mentioned Specification in fact proposes that a check valve for this purpose should be of a general form comprising a chamber having inlet and outlet openings, and a ball housed in the chamber for movement towards and away from the outlet opening, with the ball and outlet opening being formed for mutual substantial sealing engagement. In use of this valve in the Application, the inlet and outlet openings are respectively communicated with the actuator valve outlet and regulator inlet, and with the valve disposed so that the ball is normally disengaged from the outlet by gravitational force. Operation is such that the ball is moved into sealing engagement with its outlet by flow through the valve if the package is actuated when inclined significantly from the upright when, at the same time, the valve-opening effect of gravitational force on the ball is reduced.
The prior Specification proposes more specifically that its check valve have an outwardly convergently tapered outlet opening better to effect sealing engagement with the ball, and a chamber of telescopic form whereby release of the ball from such engagement is facilitated in the event of a tendency to stick. However, this is not germane to the present consideration.
Difficulty can arise with a check valve of the general form just discussed when the actuator valve is first operated because it is not primed and there is little resistance to initial flow. In these circumstances the initial surge may be so large that the ball can be moved by this alone to seal its outlet upon actuation of the package when at or close to an upright disposition. Surges at subsequent actuations can give the same effect.
An object of the present invention is to reduce this last difficulty and, to this end, there is provided a check valve for the discharge passageway of an aerosol dispensing package, comprising:
a chamber having inlet and outlet openings for in-line connection in said passageway;
a dished seat extending across said chamber between said openings with its dished surface facing towards said outlet opening; and
a ball housed in said chamber for free movement between substantial sealing engagement with said outlet opening and direct engagement in said seat;
said ball being gravitationally engaged in said seat when said chamber is in a generally upright position with said outlet opening uppermost, said seat acting to deflect discharge flow through said chamber around said ball in these last circumstances, and said dished surface being outwardly divergently shaped to cause said ball to roll therefrom under gravity and move to said sealing engagement when said chamber is inclined from said upright position by a substantially predetermined angle towards a horizontal disposition.
Also, the proposed valve preferably involves a chamber of telescopic form as more specifically proposed in the aforementioned Specification.